Particulate laundry detergent compositions of reduced or zero phosphate content containing zeolite builder are now well known and widely available.
Detergent powders normally consist of a principal homogeneous granular component, normally referred to as the base powder, containing at least organic surfactant and inorganic builder, and generally containing other robust ingredients. This may be prepared by spray-drying or by a non-tower mixing and granulation method.
Recently detergent powders containing more than one surfactant-containing ingredient (base granule) have been proposed. In particular, the art discloses powders containing a dense base granule prepared by a non-tower (non-spray-drying) mixing and granulation process, and a second base granule of lower bulk density prepared by spray-drying. The use of two different base granules enables a range of products having different bulk densities and/or different compositions to be prepared to suit differing customer needs and habits.
It has been found that compositions of this type may suffer from dispensing problems when used in European-type front-loading automatic washing machines. While dispensing devices can be used, many customers prefer to use the machine dispenser drawer and there is a demand for zeolite-built powders of all bulk densities that will dispense as well as the traditional spray-dried phosphate-built powders.
The present inventors have now discovered that dispensing of two-base or multi-base powders may be significantly improved by the inclusion of citric acid as a separate, admixed ingredient. This benefit is observed whether or not sodium carbonate is present as a separate, admixed ingredient.